Purpose :
A subset of patients with retinitis pigmentosa (RP) manifest a parafoveal annulus of increased fundus autofluorescence (FAF) that has been shown to correlate with loss of visual function encroaching upon the area within the annulus. To date, the precise source of increased FAF signal at the cellular level remains elusive. We used fundus autofluorescence adaptive optics scanning laser ophthalmoscopy (FAOSLO) to analyze FAF changes in the retina at the site of the parafoveal annulus in RP.

Methods :
Five patients with RP underwent a complete ophthalmic examination, and conventional imaging including fundus photography and FAF (HRA, Heidelberg). FAOSLO was used to image the photoreceptor and RPE layers at the single cell level across the hyperautofluorescent annulus identified by conventional FAF. Cone and rod photoreceptors were counted, and RPE segmentation was performed.

Results :
On the foveal side of the annulus, continuous photoreceptor and RPE mosaics were identified using FAOSLO. At the annulus, cones and rods were identified; cones had a dark appearance. Autofluorescence patterns within the annulus correlated to the photoreceptor images and no individual RPE cells were identified. Peripheral to the annulus, cellular patterns were disrupted in both reflectance and fluorescence images.

Conclusions :
The parafoveal annulus in RP appears to derive from the accumulation of autofluorescent material within the photoreceptors. This finding may represent a precursor to loss of visual function in patients with RP.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.